This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This project investigates (a) the development of hippocampal and perirhinal cortex functions in monkeys, (b) the long-term consequences of early insult to these brain areas on the maturation of memory processes and social bonds, and (c) the anatomical reorganization of other brain systems resulting from these early lesions as compared to adult lesions. In the current year, we have trained animals with neonatal hippocampal (Neo-H) lesions and their controls in a spatial memory foraging task, contextual memory tasks, working memory tasks, and fear learning and its modulation. Neo-H lesions resulted in robust deficits in spatial learning and working memory, although the ability to use contextual memory and to learn and modulate fear was not altered. We also validated a PET imaging protocol to assess prefrontal functioning in Neo-H animals. To pursue the characterization of animals with neonatal perirhinal lesions (Neo-PRh), we assessed object and spatial recognition memory, social interactions and emotional reactivity in Neo-PRh animals and their controls as they were adolescent. The data analyzed so far show that, unlike Neo-H lesions, Neo-PRh lesions impaired incidental recognition memory at all ages and all delays tested. However, the recognition memory deficit in Group Neo-PRh was less in magnitude than that found after Adult-PRh lesions, suggesting that the neural substrate mediating item-specific memory processes is more widespread in early infancy. Data obtained in the other tasks are being currently analyzed. Renewal of this project for another 5 years was submitted in March 2010 and awarded in December 2010.